Antimicrobial drugs such as carbapenem, new quinolone, and aminoglycoside are used for serious infections caused by opportunistic pathogens such as Pseudomonas aeruginosa. However, bacteria that have also acquired resistance to these drugs have been reported in recent years. In Japan, Pseudomonas aeruginosa that has acquired resistance to these 3 drugs is called multidrug resistance Pseudomonas aeruginosa (MDRP) and has particularly been viewed as a problem in clinical practice. It has been reported that once MDRP is separated in clinical practice, the same strain spreads in the same sickbed or hospital. This is because Pseudomonas aeruginosa is strongly viable in the natural environment and can survive in waterworks, toilets, or anywhere else water is used. Thus, even patients or medical personnel originally carrying no MDRP unintentionally carry MDRP from human carriers or living environments, possibly resulting in wide spread of the bacteria. When these carriers suffer from opportunistic infections, there may not exist an antimicrobial drug that exhibits effectiveness from the beginning. Thus, the early detection and containment of this MDRP are highly valued in clinical practice.
Metallo-β-lactamase (MBL) has been reported as one of mechanisms underlying the resistance of MDRP to carbapenem. It has been reported that carbapenem is stable for usual β-lactamase, but unstable for MBL having zinc at the active center. MBL is capable of degrading not only carbapenem but also many β-lactam agents. Many β-lactam agents are often ineffective for MBL-producing bacteria. Among MBLs, particularly, a currently controversial enzyme is plasmid-mediated MBL. The plasmid-mediated MBL was reported in Japan for the first time. However, many cases of this plasmid-mediated MBL have been reported so far not only in Japan but also in Asian and European countries. The resistance to β-lactam agents caused by MBL is now a global concern.
When MBL is present on a cyclic gene called plasmid, bacteria that have acquired this plasmid become MBL-producing bacteria. Such horizontal transmission by the plasmid is performed not only between bacteria of the same species but between bacteria of various species. For example, Enterobacteriaceae carrying this plasmid transmits the plasmid to Pseudomonas aeruginosa, which is in turn rendered resistant to β-lactam agents. In other cases, MDRP carrying this plasmid transmits the plasmid to Enterobacteriaceae, possibly resulting in the emergence of new MBL-producing enterobacteria. Thus, any of MBL-producing bacteria have the risk of causing the emergence of new multidrug resistance bacteria. Accordingly, the detection of MBL-producing bacteria is considered as an important issue in medical practice. Moreover, the identification of responsible bacteria is inevitable for the treatment of infections. When the responsible bacteria are multidrug resistance bacteria, the early selection of effective drugs and coping plans is required. In other words, when an infection by MBL-producing bacteria is suspected, early treatment can be achieved in an appropriate manner by conveniently detecting MBL. For these reasons, there has been a demand in medical practice for a method of detecting MBL conveniently, highly selectively, and highly sensitively.
Moreover, these plasmid-mediated MBLs mainly include two types: IMP and VIM types. Depending on the enzyme type, some drugs exhibit sensitivity. Thus, a drug suitable for treatment may be selected rapidly by identifying an IMP or VIM type. Furthermore, MBL inhibitor-containing antimicrobial drugs currently under study or β-lactam agents stable for MBL are considered to differ in inhibitory activity or effectiveness between IMP and VIM MBL-producing bacteria. The identification of the enzyme type is very useful for selection criteria for these drugs developed in the future. Moreover, since the gene sequences of MBL subtypes are common throughout the world, a method of identifying an IMP or VIM type can be used worldwide.
It has been required so far to use specialized machines such as PCR machines for identifying types such as IMP and VIM MBL-producing bacteria. However, simple and rapid identification is preferable for the selection of a drug. Thus, there has been a strong demand for a method of conveniently identifying a type.
Furthermore, if IMP or VIM MBL-producing bacteria can be identified without using specialized machines such as PCR machines, such identification seems to be also useful for various epidemiologic studies or for the preparation of antibiograms in individual facilities in preparation for outbreaks.
The conventional detection of MBL-producing bacteria is described in documents listed below.
Japanese Patent No. 3754993 (the head of the Infectious Disease Surveillance Center) discloses a method of determining whether or not bacteria to be detected are MBL-producing bacteria. Moreover, Japanese Patent Laid-Open Publication No. 2001-299388 (Eiken Chemical Co., Ltd.) and Japanese Patent No. 3964178 (Eiken Chemical Co., Ltd.) disclose a method of testing the drug sensitivity of MBL-producing bacteria by a broth microdilution method using the combination of a liquid medium containing a β-lactam agent and a liquid medium containing a β-lactam agentimetallo-β-lactamase inhibitor. Furthermore, Japanese Patent Laid-Open Publication No. 2004-166694 (SHOWA YAKUHIN KAKO CO., LTD.) discloses a detection method of rapidly identifying β-lactamase and a kit therefor. However, these documents neither disclose nor suggest a method of identifying a type of MBL-producing bacteria or a method of simultaneously performing the detection of MBL-producing bacteria and the identification of a type of the MBL-producing bacteria.
On the other hand, a metallo-β-lactamase inhibitor represented by the formula (I) used in the present invention is a compound disclosed in Japanese Patent No. 4122049. It is known that the compound represented by the formula (I) in combined use with a β-lactam antibiotic strengthens effectiveness for metallo-β-lactamase-producing resistance bacteria in the treatment of bacterial infection.